Dashpot: Description and Operation

Fig.11 - Throttle Valve System:

Opening of Throttle Valve

The vacuum governor on the carburetor will slightly adjust the throttle valves when driving downhill.

A two-way valve is installed in the vacuum line between the vacuum governor on the carburetor and the intake manifold, Fig. 11.

The two-way valve is controlled by the speed relay, the 30.6~F temperature switch in cylinder head and the 180~F temperature switch in thermostat housing.

Opening of Throttle Valve while Driving Downhill

At cooling water temperatures between 30.6 F and 180 F the two temperature switches are open.

If the engine speed in this temperature range increases to above 200 RPM, the speed relay will actuate the two-way valve. This will close the connection between the intake manifold and the vacuum governor and will connect the vacuum governor to the outside air.

The spring on the vacuum governor serves to adjust the throttle valves.

No Opening of Throttle Valve while Driving Downhill

If the engine speed in the temperature ranges between 30.6 F and 180 F drops below 1800 RPM, the speed relay will disconnect the current to the two-way valve. This will connect the vacuum governor to the intake manifold. The diaphragm in the vacuum governor is attracted and the throttle valves return to their idling speed position.

At cooling water temperatures below 30.6 F, the temperature switch is closed. At cooling water temperatures above 180 F, the temperature switch is closed. The speed relay and thereby the two-way valve are deenergized. This will result in a connection of the vacuum governor to the intake pipe.